Commit 6ba6b7cd authored by Dave Airlie's avatar Dave Airlie
Browse files

Merge tag 'drm/dp-aux-for-3.15-rc1' of git://anongit.freedesktop.org/tegra/linux into drm-next 

drm: DisplayPort AUX framework for v3.15-rc1

This series of patches implements a small framework that abstracts away
some of the functionality that the DisplayPort AUX channel provides. It
comes with a set of generic helpers that use the driver implementations
to reduce code duplication.

* tag 'drm/dp-aux-for-3.15-rc1' of git://anongit.freedesktop.org/tegra/linux:
  drm/dp: Allow registering AUX channels as I2C busses
  drm/dp: Add DisplayPort link helpers
  drm/dp: Add drm_dp_dpcd_read_link_status()
  drm/dp: Add AUX channel infrastructure
parents cfbf8d48 88759686

drivers/gpu/drm/drm_dp_helper.c

+395 −0
Original line number Diff line number Diff line
@@ -346,3 +346,398 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw) 
	}

}

EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);



/**

 * DOC: dp helpers

 *

 * The DisplayPort AUX channel is an abstraction to allow generic, driver-

 * independent access to AUX functionality. Drivers can take advantage of

 * this by filling in the fields of the drm_dp_aux structure.

 *

 * Transactions are described using a hardware-independent drm_dp_aux_msg

 * structure, which is passed into a driver's .transfer() implementation.

 * Both native and I2C-over-AUX transactions are supported.

 */



static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,

			      unsigned int offset, void *buffer, size_t size)

{

	struct drm_dp_aux_msg msg;

	unsigned int retry;

	int err;



	memset(&msg, 0, sizeof(msg));

	msg.address = offset;

	msg.request = request;

	msg.buffer = buffer;

	msg.size = size;



	/*

	 * The specification doesn't give any recommendation on how often to

	 * retry native transactions, so retry 7 times like for I2C-over-AUX

	 * transactions.

	 */

	for (retry = 0; retry < 7; retry++) {

		err = aux->transfer(aux, &msg);

		if (err < 0) {

			if (err == -EBUSY)

				continue;



			return err;

		}



		if (err < size)

			return -EPROTO;



		switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {

		case DP_AUX_NATIVE_REPLY_ACK:

			return err;



		case DP_AUX_NATIVE_REPLY_NACK:

			return -EIO;



		case DP_AUX_NATIVE_REPLY_DEFER:

			usleep_range(400, 500);

			break;

		}

	}



	DRM_ERROR("too many retries, giving up\n");

	return -EIO;

}



/**

 * drm_dp_dpcd_read() - read a series of bytes from the DPCD

 * @aux: DisplayPort AUX channel

 * @offset: address of the (first) register to read

 * @buffer: buffer to store the register values

 * @size: number of bytes in @buffer

 *

 * Returns the number of bytes transferred on success, or a negative error

 * code on failure. -EIO is returned if the request was NAKed by the sink or

 * if the retry count was exceeded. If not all bytes were transferred, this

 * function returns -EPROTO. Errors from the underlying AUX channel transfer

 * function, with the exception of -EBUSY (which causes the transaction to

 * be retried), are propagated to the caller.

 */

ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,

			 void *buffer, size_t size)

{

	return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,

				  size);

}

EXPORT_SYMBOL(drm_dp_dpcd_read);



/**

 * drm_dp_dpcd_write() - write a series of bytes to the DPCD

 * @aux: DisplayPort AUX channel

 * @offset: address of the (first) register to write

 * @buffer: buffer containing the values to write

 * @size: number of bytes in @buffer

 *

 * Returns the number of bytes transferred on success, or a negative error

 * code on failure. -EIO is returned if the request was NAKed by the sink or

 * if the retry count was exceeded. If not all bytes were transferred, this

 * function returns -EPROTO. Errors from the underlying AUX channel transfer

 * function, with the exception of -EBUSY (which causes the transaction to

 * be retried), are propagated to the caller.

 */

ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,

			  void *buffer, size_t size)

{

	return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,

				  size);

}

EXPORT_SYMBOL(drm_dp_dpcd_write);



/**

 * drm_dp_dpcd_read_link_status() - read DPCD link status (bytes 0x202-0x207)

 * @aux: DisplayPort AUX channel

 * @status: buffer to store the link status in (must be at least 6 bytes)

 *

 * Returns the number of bytes transferred on success or a negative error

 * code on failure.

 */

int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,

				 u8 status[DP_LINK_STATUS_SIZE])

{

	return drm_dp_dpcd_read(aux, DP_LANE0_1_STATUS, status,

				DP_LINK_STATUS_SIZE);

}

EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);



/**

 * drm_dp_link_probe() - probe a DisplayPort link for capabilities

 * @aux: DisplayPort AUX channel

 * @link: pointer to structure in which to return link capabilities

 *

 * The structure filled in by this function can usually be passed directly

 * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and

 * configure the link based on the link's capabilities.

 *

 * Returns 0 on success or a negative error code on failure.

 */

int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)

{

	u8 values[3];

	int err;



	memset(link, 0, sizeof(*link));



	err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values));

	if (err < 0)

		return err;



	link->revision = values[0];

	link->rate = drm_dp_bw_code_to_link_rate(values[1]);

	link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK;



	if (values[2] & DP_ENHANCED_FRAME_CAP)

		link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;



	return 0;

}

EXPORT_SYMBOL(drm_dp_link_probe);



/**

 * drm_dp_link_power_up() - power up a DisplayPort link

 * @aux: DisplayPort AUX channel

 * @link: pointer to a structure containing the link configuration

 *

 * Returns 0 on success or a negative error code on failure.

 */

int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)

{

	u8 value;

	int err;



	/* DP_SET_POWER register is only available on DPCD v1.1 and later */

	if (link->revision < 0x11)

		return 0;



	err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);

	if (err < 0)

		return err;



	value &= ~DP_SET_POWER_MASK;

	value |= DP_SET_POWER_D0;



	err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);

	if (err < 0)

		return err;



	/*

	 * According to the DP 1.1 specification, a "Sink Device must exit the

	 * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink

	 * Control Field" (register 0x600).

	 */

	usleep_range(1000, 2000);



	return 0;

}

EXPORT_SYMBOL(drm_dp_link_power_up);



/**

 * drm_dp_link_configure() - configure a DisplayPort link

 * @aux: DisplayPort AUX channel

 * @link: pointer to a structure containing the link configuration

 *

 * Returns 0 on success or a negative error code on failure.

 */

int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)

{

	u8 values[2];

	int err;



	values[0] = drm_dp_link_rate_to_bw_code(link->rate);

	values[1] = link->num_lanes;



	if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)

		values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;



	err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values));

	if (err < 0)

		return err;



	return 0;

}

EXPORT_SYMBOL(drm_dp_link_configure);



/*

 * I2C-over-AUX implementation

 */



static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter)

{

	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |

	       I2C_FUNC_SMBUS_READ_BLOCK_DATA |

	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |

	       I2C_FUNC_10BIT_ADDR;

}



/*

 * Transfer a single I2C-over-AUX message and handle various error conditions,

 * retrying the transaction as appropriate.

 */

static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)

{

	unsigned int retry;

	int err;



	/*

	 * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device

	 * is required to retry at least seven times upon receiving AUX_DEFER

	 * before giving up the AUX transaction.

	 */

	for (retry = 0; retry < 7; retry++) {

		err = aux->transfer(aux, msg);

		if (err < 0) {

			if (err == -EBUSY)

				continue;



			DRM_DEBUG_KMS("transaction failed: %d\n", err);

			return err;

		}



		if (err < msg->size)

			return -EPROTO;



		switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) {

		case DP_AUX_NATIVE_REPLY_ACK:

			/*

			 * For I2C-over-AUX transactions this isn't enough, we

			 * need to check for the I2C ACK reply.

			 */

			break;



		case DP_AUX_NATIVE_REPLY_NACK:

			DRM_DEBUG_KMS("native nack\n");

			return -EREMOTEIO;



		case DP_AUX_NATIVE_REPLY_DEFER:

			DRM_DEBUG_KMS("native defer");

			/*

			 * We could check for I2C bit rate capabilities and if

			 * available adjust this interval. We could also be

			 * more careful with DP-to-legacy adapters where a

			 * long legacy cable may force very low I2C bit rates.

			 *

			 * For now just defer for long enough to hopefully be

			 * safe for all use-cases.

			 */

			usleep_range(500, 600);

			continue;



		default:

			DRM_ERROR("invalid native reply %#04x\n", msg->reply);

			return -EREMOTEIO;

		}



		switch (msg->reply & DP_AUX_I2C_REPLY_MASK) {

		case DP_AUX_I2C_REPLY_ACK:

			/*

			 * Both native ACK and I2C ACK replies received. We

			 * can assume the transfer was successful.

			 */

			return 0;



		case DP_AUX_I2C_REPLY_NACK:

			DRM_DEBUG_KMS("I2C nack\n");

			return -EREMOTEIO;



		case DP_AUX_I2C_REPLY_DEFER:

			DRM_DEBUG_KMS("I2C defer\n");

			usleep_range(400, 500);

			continue;



		default:

			DRM_ERROR("invalid I2C reply %#04x\n", msg->reply);

			return -EREMOTEIO;

		}

	}



	DRM_ERROR("too many retries, giving up\n");

	return -EREMOTEIO;

}



static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,

			   int num)

{

	struct drm_dp_aux *aux = adapter->algo_data;

	unsigned int i, j;



	for (i = 0; i < num; i++) {

		struct drm_dp_aux_msg msg;

		int err;



		/*

		 * Many hardware implementations support FIFOs larger than a

		 * single byte, but it has been empirically determined that

		 * transferring data in larger chunks can actually lead to

		 * decreased performance. Therefore each message is simply

		 * transferred byte-by-byte.

		 */

		for (j = 0; j < msgs[i].len; j++) {

			memset(&msg, 0, sizeof(msg));

			msg.address = msgs[i].addr;



			msg.request = (msgs[i].flags & I2C_M_RD) ?

					DP_AUX_I2C_READ :

					DP_AUX_I2C_WRITE;



			/*

			 * All messages except the last one are middle-of-

			 * transfer messages.

			 */

			if ((i < num - 1) || (j < msgs[i].len - 1))

				msg.request |= DP_AUX_I2C_MOT;



			msg.buffer = msgs[i].buf + j;

			msg.size = 1;



			err = drm_dp_i2c_do_msg(aux, &msg);

			if (err < 0)

				return err;

		}

	}



	return num;

}



static const struct i2c_algorithm drm_dp_i2c_algo = {

	.functionality = drm_dp_i2c_functionality,

	.master_xfer = drm_dp_i2c_xfer,

};



/**

 * drm_dp_aux_register_i2c_bus() - register an I2C adapter for I2C-over-AUX

 * @aux: DisplayPort AUX channel

 *

 * Returns 0 on success or a negative error code on failure.

 */

int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux)

{

	aux->ddc.algo = &drm_dp_i2c_algo;

	aux->ddc.algo_data = aux;

	aux->ddc.retries = 3;



	aux->ddc.class = I2C_CLASS_DDC;

	aux->ddc.owner = THIS_MODULE;

	aux->ddc.dev.parent = aux->dev;

	aux->ddc.dev.of_node = aux->dev->of_node;



	strncpy(aux->ddc.name, dev_name(aux->dev), sizeof(aux->ddc.name));



	return i2c_add_adapter(&aux->ddc);

}

EXPORT_SYMBOL(drm_dp_aux_register_i2c_bus);



/**

 * drm_dp_aux_unregister_i2c_bus() - unregister an I2C-over-AUX adapter

 * @aux: DisplayPort AUX channel

 */

void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux)

{

	i2c_del_adapter(&aux->ddc);

}

EXPORT_SYMBOL(drm_dp_aux_unregister_i2c_bus);

include/drm/drm_dp_helper.h

+111 −0
Original line number Diff line number Diff line
@@ -291,6 +291,7 @@ 
#define DP_SET_POWER                        0x600

# define DP_SET_POWER_D0                    0x1

# define DP_SET_POWER_D3                    0x2

# define DP_SET_POWER_MASK                  0x3



#define DP_PSR_ERROR_STATUS                 0x2006  /* XXX 1.2? */

# define DP_PSR_LINK_CRC_ERROR              (1 << 0)
@@ -398,4 +399,114 @@ drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) 
		(dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP);

}



/*

 * DisplayPort AUX channel

 */



/**

 * struct drm_dp_aux_msg - DisplayPort AUX channel transaction

 * @address: address of the (first) register to access

 * @request: contains the type of transaction (see DP_AUX_* macros)

 * @reply: upon completion, contains the reply type of the transaction

 * @buffer: pointer to a transmission or reception buffer

 * @size: size of @buffer

 */

struct drm_dp_aux_msg {

	unsigned int address;

	u8 request;

	u8 reply;

	void *buffer;

	size_t size;

};



/**

 * struct drm_dp_aux - DisplayPort AUX channel

 * @ddc: I2C adapter that can be used for I2C-over-AUX communication

 * @dev: pointer to struct device that is the parent for this AUX channel

 * @transfer: transfers a message representing a single AUX transaction

 *

 * The .dev field should be set to a pointer to the device that implements

 * the AUX channel.

 *

 * Drivers provide a hardware-specific implementation of how transactions

 * are executed via the .transfer() function. A pointer to a drm_dp_aux_msg

 * structure describing the transaction is passed into this function. Upon

 * success, the implementation should return the number of payload bytes

 * that were transferred, or a negative error-code on failure. Helpers

 * propagate errors from the .transfer() function, with the exception of

 * the -EBUSY error, which causes a transaction to be retried. On a short,

 * helpers will return -EPROTO to make it simpler to check for failure.

 *

 * An AUX channel can also be used to transport I2C messages to a sink. A

 * typical application of that is to access an EDID that's present in the

 * sink device. The .transfer() function can also be used to execute such

 * transactions. The drm_dp_aux_register_i2c_bus() function registers an

 * I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers

 * should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter.

 */

struct drm_dp_aux {

	struct i2c_adapter ddc;

	struct device *dev;



	ssize_t (*transfer)(struct drm_dp_aux *aux,

			    struct drm_dp_aux_msg *msg);

};



ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,

			 void *buffer, size_t size);

ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,

			  void *buffer, size_t size);



/**

 * drm_dp_dpcd_readb() - read a single byte from the DPCD

 * @aux: DisplayPort AUX channel

 * @offset: address of the register to read

 * @valuep: location where the value of the register will be stored

 *

 * Returns the number of bytes transferred (1) on success, or a negative

 * error code on failure.

 */

static inline ssize_t drm_dp_dpcd_readb(struct drm_dp_aux *aux,

					unsigned int offset, u8 *valuep)

{

	return drm_dp_dpcd_read(aux, offset, valuep, 1);

}



/**

 * drm_dp_dpcd_writeb() - write a single byte to the DPCD

 * @aux: DisplayPort AUX channel

 * @offset: address of the register to write

 * @value: value to write to the register

 *

 * Returns the number of bytes transferred (1) on success, or a negative

 * error code on failure.

 */

static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux,

					 unsigned int offset, u8 value)

{

	return drm_dp_dpcd_write(aux, offset, &value, 1);

}



int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,

				 u8 status[DP_LINK_STATUS_SIZE]);



/*

 * DisplayPort link

 */

#define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0)



struct drm_dp_link {

	unsigned char revision;

	unsigned int rate;

	unsigned int num_lanes;

	unsigned long capabilities;

};



int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);

int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);

int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);



int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux);

void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux);



#endif /* _DRM_DP_HELPER_H_ */

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